1. Field of the Invention
The present invention relates to a plug socket installed on a wall surface of buildings or the like.
2. Description of the Background Art
FIG. 8 shows an exploded perspective view showing an exemplary, conventional plug socket structure. As shown in FIG. 8, a main case includes a case part 120 and a mounting element 130. The socket is formed of this main body case and a front cover 150. Case part 120 contains a terminal blade-receiving element 122 (see FIG. 10B) and a connection electrode portion (not shown) electrically connected to terminal blade-receiving element 122 to connect with an interior wiring for power supply. On the front face of case part 120, main slit 126 leading to terminal blade-receiving element 122 is provided.
Case part 120 is mounted onto a wall surface 10 of a building through mounting element 130 by means of a screw 162. Here, case part 120 is introduced into a socket-mounted hole 11 provided on wall surface 10 in advance and is then housed in wall surface 10. On the top, front cover 150 is mounted onto wall surface 10 by means of a screw 163 in order to avoid exposure of mounting element 130 on wall surface 10. Front cover 150 is provided with a plug-inserted opening 152 for exposing main slit 126 provided on the front surface of case part 120.
A terminal blade 71 of an insertion plug 70 of a power-supplied body, typically an electric appliance or the like is inserted into main slit 126 of the thus installed socket, so that the power-supplied body is powered through the plug socket.
The structure of the conventional socket will now be described. FIG. 9 is a perspective view showing the structure of case part 120 and mounting element 130 together forming the main body case. Here, case part 120 is shown mounted onto mounting element 130.
Case part 120 is formed of a rectangular parallelepiped shaped case 121 having a terminal blade-receiving face 125 on its front face, into which terminal blade 71 of insertion plug 70 is inserted. The side face of case 121 is provided with a protruding portion 124 for securing case part 120 to mounting element 130. Furthermore, plug-receiving face 125 described above is shaped such that it protrudes from the front face of case 121 by the thickness of a front cover plate 151 in order to be flush with front cover 150. In addition, at a prescribed location of plug-receiving face 125, there is formed main slit 126 into which the aforementioned terminal blade 71 of insertion plug 70 is inserted. Inside case part 120, there is arranged a leaf spring-shaped, main terminal blade-receiving element 122 electrically connected to terminal blade 71 of insertion plug 70 and rendered conductive. A main terminal blade-receiving portion 123 which is a receiving portion of main terminal blade-receiving element 122 is arranged to face the aforementioned main slit 126 (see FIG. 10B).
Now, mounting element 130 is formed of a plate 131 formed by press working and is provided at prescribed locations respectively with a latch portion 135 formed by folding back the plate and a threaded hole 136 for securing onto wall surface 10. Latch portion 135 is engaged with protruding portion 124 of case part 120 so that case part 120 is secured to mounting element 130.
A structure of a conductive portion in the conventional socket described above will now be described in detail. FIG. 10A is a front elevation showing the conventional socket attached onto the wall surface and FIG. 10B is a cross sectional view thereof taken along XBxe2x80x94XB.
As shown in FIG. 10A, at a prescribed location of front cover plate 151 of front cover 150, there is provided plug-inserted opening 152 for letting through plug-inserted face 125 formed on the front surface of case part 120. Therefore, plug-inserted face 125 is exposed to be flush with front cover plate 151. Furthermore, main terminal blade-receiving element 122 provided inside case part 120 is electrically connected with the interior wiring to enable power supply (see FIG. 10B). Main terminal blade-receiving portion 123 of main terminal blade-receiving element 122 is positioned to face toward main slit 126 so that terminal blade 71 of insertion plug 70 is brought into contact therewith and rendered conductive when inserted, thereby enabling power supply.
In the conventional socket, unfortunately, frequent insertion of the insertion plug by the user degrades and breaks the main terminal blade-receiving element for power supply. Using such a degraded or broken main terminal blade-receiving element without repair is very dangerous, may lead to an electric shock, and in addition may allegedly cause a fire resulting from abnormal heating by contact failures.
It is, however, not an easy task to determine externally whether the main terminal blade-receiving element is degraded since it is contained in the case part. Moreover, even if degradation is known, replacement is extremely dangerous for non-skilled people and therefore requires skilled experts. In addition, the structure of the conventional socket does not allow for replacement of only the main terminal blade-receiving element and thus requires replacement of the entire case part or the entire socket, which is costly. Furthermore, in the replacement work, a circuit breaker needs to be closed for safety of the workers, which is troublesome and time consuming.
An object of the present invention is therefore to provide a plug socket free from breakage of a main terminal blade-receiving element even with frequent insertion/removal of a plug, more particularly to provide a plug socket allowing for easy repair by ordinary people without special knowledge or technique.
The present invention provides a plug socket into which a terminal blade of an insertion plug is inserted frontward. The plug socket includes: an intermediate plug having an intermediate terminal blade-receiving element into which the terminal blade of the insertion plug is inserted and an intermediate terminal blade electrically connected to the intermediate terminal blade-receiving element; and a main case containing a main terminal blade-receiving element into which the intermediate terminal blade is inserted. The intermediate plug has an intermediate slit leading the intermediate terminal blade-receiving element at a front face. The main case includes a housing space having a front opening, formed with a front face and a recessed bottom face positioned to retreat backward from the front face and having a main slit leading to the main terminal blade-receiving element. The intermediate plug arranged in the housing space is interposed to connect the insertion plug with the main terminal blade-receiving element.
In this configuration, the terminal blade of the insertion plug is inserted into the intermediate terminal blade-receiving element of the intermediate plug, so that direction insertion/removal of the insertion plug into/from the main terminal blade-receiving element is eliminated, thereby preventing degradation or breakage of the main terminal blade-receiving element due to frequent insertion/removal of the terminal blade. In addition, a space for housing the intermediate plug is saved by arranging the main terminal blade-receiving element at a position recessed from the front face of the main case, so that the intermediate plug cannot be protruded from a wall surface.
Even when the terminal blade-receiving portion of the intermediate plug is broken by frequent insertion/removal of the terminal blade of the insertion plug, the entire socket needs not be replaced and only to be replaced is an intermediate plug. Furthermore, easy replacement of the intermediate plug eliminates the troublesome works conventionally required and also allows for repairs by ordinary people without special knowledge and technique. Moreover, a simple structure of the intermediate plug allows for relatively inexpensive manufacture and significantly reduces the repair cost. In addition, an electric shock or a fire due to contact failures or the like can be prevented before it happens by replacing the intermediate plug timely.
Preferably, in the plug socket in accordance with the present invention, the intermediate plug may further have an intermediate ground terminal-receiving element interposed to connect with a ground terminal and an intermediate ground terminal electrically connected with the intermediate ground terminal-receiving element. A front face of the intermediate plug may have an intermediate ground slit leading to the intermediate ground terminal-receiving element. The main case may further have a main ground slit on a recessed bottom face, into which the intermediate ground terminal is inserted.
With this configuration, it is possible to provide a plug socket adapted for an insertion plug with a ground terminal by providing the intermediate plug with an intermediate ground terminal interposed to connect with ground terminal.
Preferably, the plug socket in accordance with the present invention may further include a front cover covering the front opening of the housing space, and the front cover may have an opening exposing the front face of the intermediate plug.
With this configuration, the main case body and the intermediate plug are not exposed and the appearance of the plug socket is not impaired when installed on a wall surface. Furthermore, it is also effective that the structure inside the socket is hidden from view by the front cover so as not to expose on a wall surface for safety. It is noted that the front cover must have an opening allowing the terminal blade of the insertion plug to be inserted through the intermediate slit provided on the front face of the intermediate plug.
Preferably, in the plug socket in accordance with the present invention, the front face of the front cover may be positioned to be coplanar with the front face of the intermediate plug.
With this configuration, the front face of the plug socket is flat so that the appearance is further improved.
Preferably, in the plug socket in accordance with the present invention, an abutment portion may be provided between the front cover and the intermediate plug to bring about abutment against each other for preventing the intermediate plug from dropping-off forward.
In this configuration, the front cover abuts against the intermediate plug, so that the intermediate plug is surely secured within the housing space. Therefore, the intermediate plug can be prevented from dropping-off forward due to frequent insertion/removal of the insertion plug.
Preferably, in the plug socket in accordance with the present invention, an engagement portion may be provided between the intermediate plug and the main case to bring about engagement with each other so that the intermediate plug is guided forward and backward and secured within the housing space.
In this configuration, the intermediate plug is guided by the engagement portion, so that even ordinary people without special knowledge and technique can secure the intermediate plug within the housing space easily and repair reliably. Furthermore, this engagement portion can also function to align the intermediate plug and effectively prevent the intermediate plug from being inserted in the wrong direction.
The foregoing and other objects, features, aspects and advantages of the present invention will become more apparent from the following detailed description of the present invention when taken in conjunction with the accompanying drawings.